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 *   Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
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package org.apache.cayenne.swing.components.textpane;

import java.awt.Color;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.Shape;

import javax.swing.text.BadLocationException;
import javax.swing.text.DefaultHighlighter;
import javax.swing.text.Highlighter;
import javax.swing.text.JTextComponent;
import javax.swing.text.LayeredHighlighter;
import javax.swing.text.Position;
import javax.swing.text.View;

public class UnderlineHighlighterForText extends DefaultHighlighter {

    public UnderlineHighlighterForText(Color c) {
        painter = (c == null ? sharedPainter : new UnderlineHighlightPainter(c));
    }

    // Convenience method to add a highlight with
    // the default painter.
    public Object addHighlight(int p0, int p1) throws BadLocationException {
        return addHighlight(p0, p1, painter);
    }

    public void setDrawsLayeredHighlights(boolean newValue) {
        // Illegal if false - we only support layered highlights
        if (newValue == false) {
            throw new IllegalArgumentException(
                    "UnderlineHighlighterForArea only draws layered highlights");
        }
        super.setDrawsLayeredHighlights(true);
    }

    // Painter for underlined highlights
    public static class UnderlineHighlightPainter extends LayeredHighlighter.LayerPainter {

        public UnderlineHighlightPainter(Color c) {
            color = c;
        }

        public void paint(Graphics g, int offs0, int offs1, Shape bounds, JTextComponent c) {
            // Do nothing: this method will never be called
        }

        public Shape paintLayer(
                Graphics g,
                int offs0,
                int offs1,
                Shape bounds,
                JTextComponent c,
                View view) {
            g.setColor(color == null ? c.getSelectionColor() : color);

            Rectangle alloc = null;
            if (offs0 == view.getStartOffset() && offs1 == view.getEndOffset()) {
                if (bounds instanceof Rectangle) {
                    alloc = (Rectangle) bounds;
                }
                else {
                    alloc = bounds.getBounds();
                }
            }
            else {
                try {
                    Shape shape = view.modelToView(
                            offs0,
                            Position.Bias.Forward,
                            offs1,
                            Position.Bias.Backward,
                            bounds);
                    alloc = (shape instanceof Rectangle) ? (Rectangle) shape : shape
                            .getBounds();
                }
                catch (BadLocationException e) {
                    return null;
                }
            }

            FontMetrics fm = c.getFontMetrics(c.getFont());
            int baseline = alloc.y + alloc.height - fm.getDescent() + 1;

            int i = alloc.x;
            int end = alloc.x + alloc.width - 1;
            while (i < end) {
                g.drawLine(i, baseline, i + 2, baseline);
                g.drawLine(i, baseline + 1, i + 2, baseline + 1);
                i += 4;
            }

            return alloc;
        }

        protected Color color; // The color for the underline
    }

    // Shared painter used for default highlighting
    protected static final Highlighter.HighlightPainter sharedPainter = new UnderlineHighlightPainter(
            null);

    // Painter used for this highlighter
    protected Highlighter.HighlightPainter painter;

}